Paving systems may be used for roads, pedestrian walkways, parks, and other trafficked surfaces. In typical installations, the paving system has an exposed surface layer and fluid permeable supporting underlayers to prevent fluid (e.g. water) from pooling on the surface of the exposed layer.
The exposed surface may be stones, engineered paving stones, brick, cement, etc. and a permeable filler material, such as sand or fine crushed stone can be provided between the paving elements. Supporting fluid permeable underlayers may be composed of, for example, sand, crushed stone, pebble, gravel, or rock slabs.
In many installations, a finer grain material (e.g. sand, fine crushed stone) is used in the upper-most underlayer layer and in the filler to support the paving elements.
Typically, the particle size of the supporting underlayers is smallest in the filler material and is progressively larger in each supporting underlayer. This usually allows for laying the surface layer evenly while maximizing fluid flow.
In some installations, for example, as shown in U.S. application Ser. No. 12/713,306 to Krzyzak, “Krzyzak”, a mixed aggregate comprising a distribution of particle sizes is used in a single layer to provide a balance of stability and permeability. The mixed aggregate filler material may comprise sand, crushed stone, slabs of rock, or other fine particulate material.
In other installations, for example, as shown in Japanese publication number 2001262502 to Hiromitsu et. Al., hereinafter “Hiromitsu”, a permeable pavement structure capable of purifying seepage water using a filter layer is disclosed. However, the purifying system provided by Hiromitsu may be expensive to implement, particularly in existing paving structures. Furthermore, the effectiveness of Hiromitsu's design is dependent on many factors over which no manner of control is provided by Hiromitsu.
It is an object of the present invention to mitigate or obviate at least one of the above disadvantages.